Summary of Work: Accurate risk assessment for carcinogens requires an understanding of the link between the presence of the chemical in human tissues and the resulting biological effects of the exposure. Sensitive techniques are needed to measure the effects of exposure and for studying genetic changes that may be directly in the pathway of the disease process. Previously we have developed methods to detect both exposure-induced expression of of CYP1A1 and the Bcl-2 t(14;18) translocation. Aims: Develop biomarker technology for: 1) measuring the biological effects of exposure and early stages of disease; 2) detecting germline polymorphism; Accomplishments: 1)In order to detect early effects of TCDD exposure we used differential display to identify genes with altered expression. A novel TCDD induced gene (25-Dx) was cloned. Studies of 25-Dx expression suggest dose-dependent increase under both acute and chronic TCDD exposure. This gene is expressed in nearly all rat and human tissues and of particular interest is found in human sperm. Preliminary results suggest that the 25-Dx protein binds progesterone and is a membrane associated progesterone receptor coupled to a Ca signalling pathway. 25-Dx may be involved in TCDD's toxic reproductive effects. 2) An oligoligation based ELISA assay (OLA) for NAT1 polymorphisms was developed. Other OLAs are being developed. Automated sample handling equipment and high throughput genotyping procedures were implemented. The group is also developing new methods to assess damage from carcinogens. These studies seek to integrate environmental and genetic factors in understanding the etiology of human disease.